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Cell swelling-induced ATP release and gadolinium-sensitive channels
Francis Boudreault1, Ryszard Grygorczyk
1Centre hospitalier de l'Université de Montréal and Department of Medicine, Université de Montréal, Montréal, Québec, Canada H2W 1T8.
American Journal of Physiology. Cell Physiology
|December 18, 2001
Summary
Gadolinium (Gd3+) affects cellular ATP release differently than previously thought. Low concentrations stimulate release, while high concentrations inhibit it, suggesting complex interactions with cell membranes.
Area of Science:
- Cell Biology
- Biophysics
- Biochemistry
Background:
- Hypotonic swelling triggers widespread ATP release in eukaryotic cells.
- Mechanisms of ATP release, particularly involving mechanosensitive (MS) channels, remain unclear.
- Gadolinium (Gd3+), a known inhibitor of stretch-activated channels, was previously thought to inhibit ATP efflux.
Purpose of the Study:
- To investigate the precise effects of Gd3+ on ATP release during hypotonic swelling.
- To clarify the role of Gd3+ in modulating ATP efflux and its potential interaction with luciferase assays.
- To determine the concentration-dependent and cell-specific actions of Gd3+ on ATP release.
Main Methods:
- Utilized luciferase bioluminescence to monitor ATP efflux from hypotonically swollen cells.
- Assessed the inhibitory effects of Gd3+ on luciferase activity.
- Employed EGTA chelation to prevent Gd3+ interference with luminometric ATP measurements.
- Examined dose-dependent and cell-specific responses to Gd3+ in fibroblasts, A549, and 16HBE14o(-) cells.
Main Results:
- Gd3+ at concentrations ≤10 μM inhibited luciferase, potentially confounding previous ATP release studies.
- After accounting for luciferase inhibition, low to moderate Gd3+ concentrations (10-100 μM) stimulated ATP release in fibroblasts.
- High Gd3+ concentrations (≥100-500 μM) were required to inhibit ATP release, with varying thresholds across cell types.
- Gd3+ exhibited biphasic and cell-specific effects on hypotonic ATP release.
Conclusions:
- The previously reported inhibition of ATP release by Gd3+ may have been an artifact of luciferase inhibition.
- Gd3+ exhibits complex, concentration-dependent, and cell-specific modulation of hypotonic ATP release.
- These findings suggest Gd3+ acts on membrane lipids and membrane-dependent processes like exocytosis, rather than solely blocking MS channels.